Apparatus for sharpening rotary cutters



July 4, 1967 H. WARD APPARATUS FOR SHARPENING, ROTARY CUTTERS 6Sheets-Sheet 1 Filed June 12, 1964 lnvenlor fi flzz 40 :4

July 4, 1967 H. WARD APPARATUS FOR SHARFENING ROTARY CUTTERS 6Sheets-Sheet 2 Filed June 12, 1964 I nvenlor H1919? ddmafi y M M gzz; ABarneys Jul 4, 1967 H, WARD 3,328,924

APPARATUS FOR SHARPENINGROTARY CUTTERS Filed June 12, 1964 6Sheets-Sheet 5 I W FJ l lnver ztor /7 A ?R) (AJA RoL A ttorneys y 4,1967 H. WARD 3,323,924

APPARATUS FOR SHARPENING ROTARY CUTTERS Filed June 12, 1964 6Sheets-Sheet 4 A ttorneyg July 4, 1967 H. WARD APPARATUS FOR SHARPENINGROTARY CUTTERS 6 Sheets-Sheet 5 Filed June 12, 1964 Rah-.5?? k 9 5. x i2 I iIEEEEEEi.

Invenlor HARR) Afl Attorneys July 4, 1967 H. WARD APPARATUS FORSHARPENING ROTARY CUTTERS Filed June 12, 1964 6 Sheets-Sheet 6 9 ap-LEEa; H L

Inventor 644KB Q/A Rd.

. B Q 6%, Attorneys United States Patent 3,328,924 APPARATUS FORSHARPENIN G ROTARY CUTTERS Harry Ward, London, England, assignor, bymesne assignments, to AME International Limited, London, England FiledJune 12, 1964, Ser. No. 374,645 Claims priority, application GreatBritain, June 13, 1963, 23,637/ 63 7 Claims. (Cl. 51-249) This inventionrelates to the sharpening by grinding of rotary cutters of the typehaving one or more knives whose cutting edges can be definedgeometrically as lying in a cylindrical surface whose axis is the axisof rotation of the cutter. In many such cutters the cutting edges areparallel to the axis, but they may lie on helices or on any other lineslying in the cylindrical surface.

According to the invention, a machine having a rotary cutter rotatingabout an axis and having one or more knives with cutting edges lying ina cylindrical surface, further has means for sharpening the knivescomprising a disc grinding wheel mounted for rotation about an axissubstantially perpendicular to a plane containing the axis of the rotarycutter, the rim of the grinding wheel being hollowed to match thecylindrical surface, and a carriage on which the grinding wheel ismounted and which is arranged to reciprocate along the full length ofthe cutting edges parallel to the axis of the cutter and to dwell at oneend of its reciprocating movement, and a dresser for maintaining thecontour of the hollowed rim of the grinding wheel, mounted on an armwhich is pivoted about an axis parallel to, adjacent to, and adjustablewith respect to, the axis of the rotary cutter, at the end of the cutterat which the carriage dwells.

In the preferred arrangement, the dresser is a diamond, which is mountedon the end of an arm whose other end is pivotally mounted on aneccentric sleeve, which is itself mounted coaxially with the rotarycutter.

This invention is particularly applicable to machines of the rotary drumtype used for cutting leaf tobacco. In these machines the cutter has aconsiderable number of knives slightly skew to the axis and equallyspaced around its circumference. These machines present the advantagethat if the knives are closely spaced around the circumference of thecutter, the cutting is practically continuous and so the output of cuttobacco is high. In order to make this output as high as possible, theknives must 'be kept constantly sharp by grinding them while the machineis working. At the same time the knives must move as fast as possible,consistent with good cutting, for the same reason. Accordingly theproblem that arises in makingsuch a machine is to ensure that thegrinding wheel will remove some metal from the cutting edges of theknives, without distorting or overheating them and without producingrapid Wear of the grinding wheel, in an extremely limited time. If thegrinding action has to take place too quickly, both the cutting edgesand the wheel suffer.

The grinding wheel is arranged on the opposite side of the cutter fromthe mouthpiece through which the tobacco is fed, and the cutter isrotated so that the knives pass down across the mouthpiece, and upwardsacross the rim of the grinding wheel. As the cutting edges of the knivesare continuously sharpened, metal is worn away from them, and at thesame time the rim of the grinding wheel is worn away. In order tocompensate for this wear, the knives are fed progressively outwards fromthe cutter. A particular mechanism for carrying this out is described inBritish Patent No. 665,653, for example. The knives are moved outwards asmall distance at each end of the reciprocating movement of thecarriage, when the grinding wheel is just clear of the cutting edges.

To take account of the wear of the grinding wheel which slowly decreasesits diameter, the wheel is fed in towards the cutter, each time thecarriage reaches the end of the cutter at which the dresser is mounted.

The accompanying drawings show the relevant parts of one example of atobacco cutting machine constructed in accordance with this invention.In these drawings:

FIGURE'l is a side view of the drum and grinder mechan-ism, with partsin section on the line I-I in FIGURE 2;

FIGURE 2 is a rear view, i.e., a view from the left in FIGURE 1, withmost of the drum, and rear portions of the uprights, main beam, andgrinder housing broken away;

FIGURE 3 is a fragmentary section on the line IIIIII in FIGURE 2;

FIGURE 4 is an enlarged fragmentary section on part of the line IV-IV inFIGURE 2;

FIGURES 5 and 6 are sections on the line VV in FIGURE 4, showingdifferent operating positions; and

FIGURE 7 is an exaggerated diagram showing the action of the dresser.

As shown in FIGURE 1, the machine includes upper and lower conveyors 2and 4 which deliver leaf tobacco through a mouthpiece 6. As the tobaccoemerges from the mouthpiece, moving towards the right in FIGURE 1, it issliced by knives 8 on the drum 10. This drum rotates at high speed on ashaft 12. It is supported by two uprights 14 which are pivoted to themain frame of the machine at 16, and which are very precisely adjustedin position in relation to the mouthpiece by means which are not shownas they do not directly concern the present invention.

The two uprights 14 are linked by a main 'beam 18 from the two ends ofwhich there extend forward projections '20, which support two tubularrails 22. On these rails there slides a carriage 24 carrying a grinder.This grinder includes a disc grinding wheel, 26, a motor 28, and a beltdrive 30. As shown in FIGURE 2, the grinding wheel 26 a is on a verticalshaft 32 mounted in an arm 34 which can swing about a vertical post 36under the control of adjusting mechanism 38 which acts between a housing40 fixed to the carriage 24 and two lugs 42 fixed to the arm 34. Thegrinding wheel is exposed towards the drum 10, but is otherwise enclosedwithin a housing 44 which is supported from the carriage 24 by pillars46. The primary function of the mechanism 38 is to shift the grindingwheel gradually rearwards (i.e., to the left in FIGURE 1 to make up forthe gradual wearing away of the grinding wheel.

The carriage 24 is reciprocated by mechanism shown in FIGURES 1, 2 and3, housed within the main beam 18. This consists of a slot 47 in thecarriage, engaged by a follower roller 48 projecting from a chain 50which has two runs parallel to the path of the carriage and which passesround a large driving wheel 52 at one end and two small wheels 54 at theother end. It will be seen that, while the follower 48 is movingvertically between the two small wheels 54, there will be a dwell in themotion of the carriage. During this dwell the grinding wheel will lie inalignment with a dressing unit 56 at the right hand end in FIGURE 2.

This dressing unit, as shown in FIGURES 1, 2 and 7, consists of adiamond 58 mounted on an arm 60 which is pivoted around a sleeve 62.This sleeve 62 is eccentric, and is itself mounted coaxially with therotary cutter 10, by being journalled on a fixed bush 64 surrounding thecutter shaft 12. The normal position of the diamond 58 is just below thelevel of the bottom of the grinding wheel 26. Each time the grindingwheel reaches the dwell point, the diamond is automatically swungupwards across the face of the grinding wheel by mechanism shown in FIG-URES 1 and 2.

As shown in FIGURE 2, two levers 68 and 70 are pivoted to the main beam,and connected by a link 72 which also carries a cam 74. As shown inFIGURE 3, the follower roller 48 is associated with a second followerroller 76, and, as this roller 76 moves downwards between the wheels 54,it strikes the cam 74 and displaces it to the right, as seen in FIGURE2. This movement is transmitted by a rod 78, acting against a spring 80,to a bellcrank 82, and thence by a link 84 to the arm 60 carrying thediamond (see FIGURE 1). When the grinding wheel commences its nextmovement to the left, as seen in FIG- URE 2, the diamond returns to itsnormal position.

Just as the grinding wheel reaches the dwell point, it is moved slightlyto the left, as seen in FIGURES 1 and 4, by the mechanism shown inFIGURES 4 and 5. As the carriage 24 reaches the dwell point, an abutment86 on an arm 88 strikes a fixed abutment 90'. The arm 88 is fixed to ashaft 92, and is normally held in the position shown in chain lines inFIGURE by means of a torsion spring 93 (FIGURE 4). The shaft 92 carriestwo pawls 94 which cooperate with two ratchet wheels 96 and 98. Theratchet wheel 96 has one tooth less than the ratchet wheel 98. The wheel96 is screw threaded on to an axle 100, and the wheel 98 is mountedintegrally on a sleeve which is keyed to the axle at 102. The positionof the ratchet wheel 96 is fixed axially, so that when both ratchetwheels are rotated through one tooth interval, by means of the pawls 94,the axle 100 is moved to the left in FIGURE 4 by a small amount whichcorresponds to the difference in angular pitch of the teeth of theratchet wheels, and which also depends on the pitch of the screw.

At the end of each stroke of reciprocation of the carriage, the knives8, which are flat, are each fed in the direction of their own plane, soas to project slightly further from the drum, and thus make up for wear,and also provide a small amount of material to be ground away during thenext reciprocation of the grinding wheel, and thereby present a freshsharp edge. For example, the feed mechanism may, as indicated in FIGURE1, include a pneumatic cylinder 104 associated with each knife, thecylinders being supplied with a pulse of air through a central passage106 each time the carriage 24 concludes a stroke.

Before the machine is put into continual use, the following initialadjustments are made. First the knives 8 are set so that they projectfrom the cutter a desired amount, i.e. so that they sweep out a cylinderpath having a desired small clearance from the front of the mouthpiece6. The cutter and the grinding wheel are then set in rotation, and withthe carriage stationary, the grinding wheel is fed forwards by handtowards the cutter until grinding commences, and is occurring throughoutthe depth of the rim of the wheel. This will mean that, as shown inFIGURE 7, the knives, which move upwards past the grinding wheel, willapproach the grinding wheel with edges at a radius A from the cutteraxis X, and will leave the grinding wheel with their edges at a slightlysmaller radius B from the axis X. To achieve this action progressively,the profile of the grinding wheel should be an arc struck from a centresomewhat below the axis X. How this situation is maintained will bedescribed below.

The feeding forward of the grinding wheel during this initial setting iscarried out as shown in FIGURES 4 and 6. That is to say, the abutment 86is swung downwards so that the arm 88 swings further to the left thanits normal position. This carries the pawls 94 out of engagement withthe ratchet wheels 96 and 98, and at the same time brings a locking pawl108 into engagement with the ratchet wheel 96 only. The sleeve which iskeyed to the shaft may then be rotated by a hand wheel 110, producing arelatively rapid feeding movement of the grinding wheel. At theconclusion of this, the arm 88 is pulled to the right in FIGURE 6, andthe abutment 86 is restored to its normal position.

The carriage is then run to its dwell point, so that the grinding wheelis abreast of the dresser, and the arm of the dresser is swung manuallyupwards. Adjustments are made both by angular movement of the eccentricsleeve 62 and by radial adjustment of the diamond 58 relative to the arm60, by means of a screw thread and locking nuts 112. Movement of thesleeve 62 (which can then be locked to the bush 64 by means not shown)causes the pivot axis Y of the diamond 58 to rotate around the cutteraxis X. Adjustment at 112 changes the radius from the diamond 58 to thepivot axis Y. By a combination of these adjustments, the diamond iscaused just to contact the grinding wheel throughout the depth of theface of the grinding wheel. That is to say the diamond travels throughthe are necessary to maintain the profile of the grinding wheel whichgives the progressive knife sharpening action described above. Nofurther adjustment of the eccentric sleeve 62 should then be required.

To provide a check on any wear of the diamond 58, the diamond is thenswung by hand to an upright position indicated at 114, and an adjustablescrew 116 in a bracket fixed to the upright 14 is turned until it justtouches the diamond. This then provides a datum against which thediamond can be checked from time to time. If the diamond should becomeworn, then it may be brought back into contact with this datum by theadjustment 112.

The machine can then be put into continuous use.

It will be found that the optimum position of the axis Y about which thediamond pivots is slightly below and forward from the axis X of thecutter.

I claim:

1. In a machine having a rotary cutter rotating about an axis and havingone or more knives with cutting edges lying in a cylindrical surface,means for sharpening said rotary cutter comprising a disc grinding wheelmounted for rotation about an axis substantially perpendicular to aplane containing the axis of the rotary cutter, the rim of the grindingwheel being hollowed to match the cylindrical surface, a carriage onwhich the grinding wheel is mounted and which is arranged to reciprocatealong the full length of the cutting edges parallel to the axis of thecutter and to dwell at one end of its reciprocating movement, and adresser for maintaining the contour of the hollowed rim of the grindingwheel, mounted on an arm which is pivoted about an axis parallel to,adjacent to, and adjustable with respect to, the axis of the rotarycutter at the end of the cutter at which the carriage dwells.

2. A machine according to claim 1, in which the dresser is a diamond,which is mounted on the end of an arm whose other end is pivotallymounted on an eccentric sleeve, which is itself mounted coaxially withthe rotary cutter.

3. A machine according to claim 2 including means for adjusting theangular position of the sleeve, and means for adjusting the effectiveradius of the dresser tip.

4. A machine according to claim 1, further comprising means forautomatically swinging said dresser across the face of the grindingwheel each time the grinding wheel reaches the dwell point.

5. A machine according to claim 1, in which the axis of the rotarycutter is horizontal, further comprising means for driving the rotarycutter in the sense that the cutting edges move upwards past thegrinding wheel, the pivot axis of the dresser being slightly below theaxis of the cutter, so that the grinding wheel has a progressive actionon each knife as it passes.

6. A machine according to claim 1, in which the motion of reciprocationand dwell is imparted to the carriage by a slot on the carriage engagedby a follower projecting from a chain which has two runs parallel to thepath of the carriage and which passes round one large wheel at one endof the runs and two small wheels at the other end.

7. A machine according to claim 1, further comprising difierential screwand ratchet means for automatically feeding said grinding wheel towardthe cutter each time said grinding wheel reaches the dwell point.

References Cited UNITED STATES PATENTS 2,121,879 6/1938 Lorentz 5l2492,327,272 8/1943 Jones 1 125-41 2,476,177 7/1949 Bloom 146l17 2,479,1018/1949 Dahl 12511 2,738,629 3/1956 Schreiber 51249 2,830,634 4/1958Pollrnan 51-249 X ROBERT C. RIORDON, Primary Examiner. LESTER M.SWINGLE, D. G. KELLY,

Assistant Examiners

1. IN A MACHINE HAVING A ROTARY CUTTER ROTATING ABOUT AN AXIS AND HAVINGONE OR MORE KNIVES WITH CUTTING EDGES LYING IN CYLINDRICAL SURFACE,MEANS FOR SHARPENING SAID ROTARY CUTTER COMPRISING A DISC GRINDING WHEELMOUNTED FOR ROTATION ABOUT AN AXIS SUBSTANTIALLY PERPENDICULAR TO APLANE CONTAINING THE AXIS OF THE ROTARY CUTTER, THE RIM OF THE GRINDINGWHEEL BEING HOLLOWED TO MATCH THE CYLINDRICAL SURFACE, A CARRIAGE ONWHICH THE GRINDING WHEEL IS MOUNTED AND WHICH IS ARRANGED TO RECIPROCATEALONG THE FULL LENGTH OF THE CUTTING EDGES PARALLEL TO THE AXIS OF THECUTTER AND TO DWELL AT ONE END OF ITS RECIPROCATING MOVEMENT, AND ADRESSER FOR MAINTAINING THE CONTOUR OF THE HOLLOWED RIM OF THE GRINDINGWHEEL, MOUNTED ON AN ARM